About multiple versions of the same gem: there is a gem called Bundler (http://gembundler.com)? It allows you to create a Gemfile for your project, describing which gem and which version you need for your project to run. When you enter the command:

$ bundle install

It installs the required versions of the required gems, specified in your Gemfile. When you run:

$ bundle exec <command>

It runs the <command> using the specified version of each gem. So, you can keep multiple versions of the gems, and choose which one to use in a particular project.

On 12 December 2012 15:16, Bardur Arantsson <spam@scientician.net> wrote:

On 12/12/2012 06:01 PM, Janek S. wrote:
> In the recent months there was a lot of dicussion about cabal, dependency hell and alike. After
> reading some of these discussions there is a question I just have to ask:
>
> Why not create a package manager (like rpm or apt) for Haskell software?
>
> I've been using Linux for years. Software for Linux is mostly written in C and C++. There are
> thousands of libraries with lots of dependencies and yet:
> a) Linux distributions manage to have package repositories that are kept in a consistent state
> b) Linux package managers can avoid dependency hell, automatically update to new packages, etc.
> Linux people did it! Is there any technical issue that prevents Haskell people from doing exactly
> the same thing? Or are we just having non-technical problems like lack of money or developers?
>

Well, one big issue is that Linux distribution packagers have control of
the entire stack. A (hypothetical) Haskell package manager wouldn't.

Typical package managers also restrict you to exactly one version of any
given package. This can be a severe limitation for developers.

(There are more issues.)

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Andre Cunha